The flag for use on land is a white ensign (without cross) with the arms of the territory, quite large, in the fly. The flag is for flying at British Antarctic bases (which previously flew the British flag) and at the British Antarctic Survey headquarters in Cambridge, England. I have also suggested that it be flown at the Discovery Centre in Dundee, where the RRS Discovery is moored, next to an Antarctic exploration museum. The RRS Discovery was the ship that first carried Captain Scott to the pole in 1901 and on further expeditions. She is the ship that forms the crest of the arms of the British Antarctic Territory.
Graham Bartram, 31 October and 1 November 1998

Roman Klimes' paper 'Symbols of Antarctica', published in [icv97], pp. 232-237, gives the official description of the coat of arms of the British Antarctic Territory:

On 11 March 1952, the Falkland Island Dependencies (constituted in 1908, divided in 1963 into British Antarctic Territory and South Georgia and South Sandwich Islands) were granted arms by Royal Warrant:

Arms: Per fess wavy barry, wavy of six Argent and Azure, and Argent on a Pile Gules, a Torch enflamed proper.
Supporters: In Dexter a Lion Or and in Sinister an Emperor Penguin proper upon a compartment divided per pale and representing in Dexter a grassy Mount and in Sinister an ice Floe.
Motto: Research and Discovery.

This coat of arms was transferred to the B.A.T. on 1 August 1963, with the addition of helm, crest and mantling:

Mantling: in Dexter Or doubled Gules and in Sinister Argent doubled Azure. Crest: Upon a Wreath of the colours of the Mantling a representation of the research Ship Discovery.

The Blue Ensign with the arms of the B.A.T. in the fly was introduced by Royal Warrant on 30 May 1969.
Ivan Sache, 2 May 2001

Graham Bartram's image of this ensign (and several
others) shows the reverse of the flag as almost mirrored, but with the lettering
of the motto reading correctly (un-mirrored). Dean McGee, 2 July 2006

I'm being ultra picky here but there are a couple of problems with the crest
on this flag as drawn. Discovery has a smoke stack, she is a steam ship with
masts, not a sailing ship. Her blue ensign is plain, undefaced - there appears
to be a white dot where a badge would be.Graham Bartram, 17 August 2006

The white ensign and the Commissioner's flag were authorized by Her Majesty
The Queen on 21 April 1998.Christopher Southworth, 9 October 2006

Based on information on World Flags Database.
The ribbon below everything on this shield reads correctly while the rest of the
badge is a mirror image of the obverse. I have seen only one British made copy
of the BAT white ensign, and it was all printed, meaning that the ribbon read
backwards on the reverse side. I would imaging "official" batches of flags have
the ribbon reading correctly on the back side.Clay Moss, 15 August 2006

The blue ensign is still in use. I know this as I am a consultant to
the Foreign Office Polar Regions Section. The blue ensign with shield
remains the government ensign of the British Antarctic Territory and is
therefore flown by vessels undertaking work on behalf of the British
Antarctic Territory authorities, which includes those vessels working
for/with the British Antarctic Survey.

The new white ensign is not intended for use at sea, but lacking a civil
ensign (there is a strange lack of civil vessels registered in British Antarctic
Territory) then a civilian vessel visiting British Antarctic Territory would
fly it as the courtesy ensign. Foreign government vessels should fly the defaced
blue ensign. The Commissioner's flag could of course be flown as a rank flag by
any vessel carrying the Commissioner, but not as an ensign.
Graham Bartram, 2 November 1998

BAT has a Blue Ensign (in addition to/predating the white with full arms),
and this was established by Royal Warrant dated 30 May 1969.Christopher Southworth, 14 June 2005

The arms of British Antarctic Territory, as shown, differ in several respects
from the coat of arms displayed on the flag. Differences:

The ship on the crest is brown with black unadorned masts on the coat of
arms; it is black with yellow masts and white sails on the flag.

The wreathing round the helm is halved blue and white/red and yellow on
the arms; it is entirely blue and white on the flag.

The helm is entirely grey on the arms; it is shaded with black and
yellow on the flag.

The penguin is unshaded on the coat arms, and has a yellow bill and
feet; the penguin on the flag is shaded, the bill is red, the feet are
black, and it has a yellow collar (the flag is more zoologically accurate, I
think).

The lion's teeth are bared on the coat of arms - this is not apparent on
the flag.

The base shows no texture or colour variation on the coat of arms, and
its edge is plain white; the grass is textured, the penguin's shadow is
visible, and its edge is yellow on one half and shaded white and ice blue on
the other.

The scroll is white on the coat of arms with grey shading where it
rolls; it is yellow on the flag, with red shading where it rolls.

James Dignan, 6 August 2008

The official model of the flag of BAT
differs from the original College of Arms painting in a number of respects, all
of which concern the RRS Discovery that forms the crest. The College had given
her a Red Ensign when it should have been a Blue (Royal research ships wear an
undefaced Blue Ensign), they had forgotten the funnel of this steamship, and had
put a yard on the mizzen mast when she is gaff rigged on the mizzen.

There is one more difference between the signed painting and the official model
- the College of Arms had used an army-style Union in the canton! This adds the
fimbriation on the red diagonals to the outside of the red, rather than cutting
into it, making each blue triangle a different shape! This was replaced by a
standard naval-style Union.Graham Bartram, 6 August 2008

I have on file a copy of the College of Heralds' illustration for the flag
signed (thus approved) by Her Majesty and upon which Graham tells me he based
the definitive illustration in BR20 - which may be seen on his website at
http://www.flags.net/BANT.htm. From
this we may see that, howsoever accurate (or not) Clay's illustration of the
arms may be, his image of the flag very closely follows the definitive model and
is thus correct.Christopher Southworth, 6 August 2008

According to Crampton's Observer's Book of Flags the British
Antarctic Territory arms are "an embellished form" of the arms of the
Falkland Islands Dependencies granted in 1953. This was when the
Falkland Islands Dependencies still included British Antarctica and was
a separate entity from the Falkland Islands proper.
When the British Antarctic Territory was founded in 1962 the remaining parts
of the Falkland Islands Dependencies (South Georgia and the South Sandwich
Islands) reverted to the Falkland Islands. However, since the Falklands
War, a new territory of South Georgia and the South
Sandwich Islands was founded in 1985.
Roy Stilling, 5 December 1995

The flag of the commissioner of the British Antarctic Territory is a Union
flag defaced with a white disc with a gold edge, covered by a laurel wreath,
with the full achievement of arms in the centre. An interesting feature is the
gold ring under the laurel. I have seen references to the governor of Gibraltar's
flag where the presence of the gold ring is associated with the gold border that
sometimes appears on the Gibraltar arms. I suspect from this flag, that all
governor/commissioner flags that bear a laurel wreath are meant to have a gold
ring under them.

I don't think the Commissioner of the British Antarctic Territory is the
same person as the governor of the Falklands. As far as I know the Falklands, has
a resident governor, whereas the British Antarctic Territory's commissioner is
head of the Polar Regions Department of the Foreign and Commonwealth Office in
London. I'm not sure where or when he'll use his flag.
Graham Bartram, 31 October and 1 November 1998

British Antarctic Survey operates throughout the Antarctic region, in more
than one British Overseas Dependent Territory. It supports three stations in the
Antarctic, at Rothera Point Adelaide Island, Halley and Signy Island (summer
only), and two stations on South Georgia, at King Edward Point and Bird Island.
The Antarctic operations and science programmes are managed from Cambridge in
the United Kingdom.

Further information on each of these research stations and the work of BAS more
generally, can be found here:
http://www.bas.ac.uk. Colin Dobson, 5 June 2005